1. Field of the Invention
The present invention relates to a speed change apparatus of a vehicle including a gear transmission, a shift lever device arranged in a zone where an operation thereof is achievable from a driver's seat, and an operation force transmission mechanism for transmitting an operation force of the shift lever device to the gear transmission.
2. Description of the Prior Art
FIG. 10 shows a speed change apparatus according to a conventional art described in JP Laid-open Publication No. 2006-082737. A shift mechanism 300 of a gear transmission T includes a shift shaft 302 supported by a transmission case 301 so as to be movable in an axial direction, a shift fork 303 fixed to the shift shaft 302, and a shift sleeve 306 engaging with the shift fork 303. The shift sleeve 306 is spline-fit onto a speed change shaft 305 so as to be movable in the axial direction. The shift fork 303 is connected to a shift lever device (not shown) through a drive pin 310, an inner lever 311, a lever shaft 312, an outer lever 313, and an operation force transmission mechanism 314. The shift mechanism 300 includes only one detent mechanism 320 for positioning and holding the shift shaft 302 at each shift position in the axial direction.
The detent mechanism 320 comprises a plurality of recesses 321 formed in an outer peripheral surface of the shift shaft 302, a detent ball 322 for engaging selectively with each recess 321, and a coil spring 323 for pushing the detent ball 322 against the outer peripheral surface of the shift shaft 302.
As shown in FIG. 10, in a configuration that only one detent mechanism 320 positions and holds the shift shaft 302 in an inside of the transmission case 301, in order that a force of holding the shift shaft 302 at each shift position should be increased, a spring load of the coil spring 323 need be increased. This requires a coil spring having a larger wire diameter and a larger coil diameter as well as an accommodation space for this. This causes size increase in the transmission case 301. Further, since one site in the axial direction of the shift shaft 302 is strongly pressed in a radial direction, a force acting in a direction of inclining the shift shaft 302 increases. Thus, a sliding resistance of the shift shaft 302 increases and hence a larger shift operation force becomes necessary.